1. Field of the Invention
This invention relates to writing instruments and, more particularly, to writing instruments adapted to simultaneously project or retract upper and lower members from opposite open ends of a barrel.
2. Description of the Prior Art
Writing instruments having a twist-type mechanism capable of projecting or retracting writing medium assemblies such as pen nibs from opposite open ends of a barrel are well known in the art. However, such writing instruments require a relatively complicated and expensive project or retract mechanism. Some of the prior art writing instruments also rotate the pen nibs during displacement and cause the pen nibs to scrape and wipe ink against the inside surface of the barrel. The collected ink on the inside surface of the barrel could eventually foul the pen nib.
Accordingly, it is desired to provide a writing instrument with a relatively simple and inexpensive project or retract mechanism capable of simultaneously projecting or retracting writing medium assemblies from opposite open ends of a barrel without scraping against an inside surface of the barrel.